A spoolable pipe in common use is steel coiled tubing which finds a number of uses in oil well operations. For example, it is used in running wireline cable down hole with well tools, such as logging tools and perforating tools. Such tubing is also used in the workover of wells, to deliver various chemicals downhole and perform other functions. Coiled tubing offers a much faster and less expensive way to run pipe into a wellbore in that it eliminates the time-consuming task of joining typical 30 foot pipe sections by threaded connections to make up a pipe string that typically may be up to 10,000 feet or longer.
Steel coiled tubing is capable of being spooled because the steel used in the product exhibits high ductility (i.e. the ability to plastically deform without failure). The spooling operation is commonly conducted while the tube is under high internal pressure which introduces combined load effects. Unfortunately, repeated spooling and use causes fatigue damage and the steel coiled tubing can suddenly fracture and fail. Such a potential hazard of the operation and attendant risk to personnel, plus the high economic cost of such a failure in down time to conduct fishing operations, forces the product to be retired, before any expected failure, after a relatively few number of trips into a well. The cross section of steel tubing expands during repeated use resulting in reduced wall thickness and higher bending strains with associated reduction in the pressure carrying capability. In general steel coiled tubing presently in service is limited as to internal pressures of about 5000 psi. Higher internal pressure significantly reduces the integrity of coiled tubing so that it will not sustain continuous flexing and thus severely limits its service life. At very high working pressures the coiled tubing may be limited to a single field application. The initial state of the coiled tubing used in these operations is in a spooled condition on a reel. Three bending events occur going into the wellbore and three upon on its retrieval. In general service work it is common to cycle in and out of the well over short intermediate intervals. When the internal pressure in steel body of the pipe is above 30 percent of the tubing yield rating, when it is bending, significant plastic deformation takes place in the pipe.
It is therefore desirable to use a substantially non-ferrous composite spoolable pipe capable of being deployed and spooled under borehole conditions and which does not suffer from the structural limitations of steel tubing and which is also highly resistant to chemicals. Such spoolable pipe products are now being developed and are generally constructed by imbedding fibrous materials in a resin matrix. These products typically utilize a build up of laminate layers with the fibers in each layer oriented in a particular direction (or directions when a fabric or braided construction is used). Such pipe is described in SPE paper #26536 entitled "Development of Composite Tubing for Oilfield Services", by Sas-Jaworsky and Williams, Copyright 1993, Society of Petroleum Engineers, Inc.
An injector system is used to inject and retrieve spoolable pipe from a wellbore in such oilfield services. A part of the injector system is a stripper device using elastomeric elements to sealingly engage the outer surface of the pipe as it is injected into or pulled out of the well. These sealing elements isolate the higher pressure borehole environment from the ambient surface pressure. The functional engagement of the injector mechanism and of these sealing elements in the stripper with a composite pipe, tends to damage the surface integrity of a composite material, which can cause wellbore fluid pressure to bypass the stripper. When composite pipe is used in these applications, repeated bending of the composite materials as well as frictional engagement of the pipe with the stripper elements may cause fissures to form in the surface of the composite pipe. It is desirable to diminish the frictional disturbance between the outer surface of the pipe and these stripper elements. It is therefore an object of the present invention to provide a new and improved method and apparatus for applying and infusing a treating material into the outer surface of a spoolable composite pipe to reduce friction and the consequences of fissures caused by repeated stressing of the composite pipe in use.